fix(node:v8): Serializer/Deserializer classes + lifecycle/diagnostic namespaces

[proggeramlug]

Closes #3680
Closes #3679

Implementation

Builds on the existing node:v8 surface (v8.serialize/deserialize/heap-stats/GCProfiler) in crates/perry-runtime/src/node_v8.rs.

#3680 — v8.Serializer / v8.Deserializer classes

• new v8.Serializer() / new v8.DefaultSerializer() / new v8.Deserializer(buf) / new v8.DefaultDeserializer(buf) now construct real, stateful instances backed by the structured-clone codec that already powers v8.serialize/deserialize (child_process::v8_serde).
• Each instance is a NATIVE_MODULE_CLASS_ID namespace object carrying a registry id in field[1] (mirrors the PerformanceObserver instance pattern) — no new HIR/codegen variant. Instance method calls route through dispatch_native_module_method.
• Methods: writeHeader/writeValue/writeUint32/writeUint64/writeDouble/writeRawBytes/releaseBuffer and readHeader/readValue/readUint32/readUint64/readDouble/readRawBytes.
• A new OwnedDeserializer keeps the input buffer alive across method calls (the codec's internal Deserializer only borrows). GC suppression wraps each writeValue/readValue walk.
• typeof v8.Serializer === "function" via the native-callable-export path; construction is statically lowered in expr/new_dynamic.rs.

#3679 — lifecycle / diagnostic-control namespaces

Perry has no V8 engine to drive real snapshots / coverage / promise-lifecycle hooks, so these expose Node's observable shape only:

• v8.startupSnapshot namespace: isBuildingSnapshot() returns the number 0 (matching Node, not a boolean); addSerializeCallback/addDeserializeCallback/setDeserializeMainFunction throw ERR_NOT_BUILDING_SNAPSHOT like Node.
• v8.promiseHooks namespace: onInit/onBefore/onAfter/onSettled/createHook return a no-op stop callable.
• Top-level setFlagsFromString/takeCoverage/stopCoverage/setHeapSnapshotNearHeapLimit are Node-shaped no-op callables returning undefined.
• Both the chained method-call form (folded to NativeMethodCall { class_name: Some("startupSnapshot") }) and the value-read form (typeof v8.startupSnapshot.isBuildingSnapshot) are handled.

Dropped (correctly): real getHeapSnapshot/writeHeapSnapshot stream/file emission, real coverage capture, real promise-hook lifecycle — these require a V8 engine. They are coordinated with #3140 rather than faked here; only correctly-shaped no-op surface is exposed.

Manifest + generated docs (docs/api/perry.d.ts, docs/src/api/reference.md) updated; regen_api_docs.sh re-run.

Validation

• Gap test test-files/test_gap_v8_2_3680plus.ts is byte-identical to node --experimental-strip-types under the default auto-optimize compile (Serializer/Deserializer round-trip asserted via deep JSON.stringify equality, not raw bytes).
• Prior v8 gap test test_gap_node_v8_3137plus.ts remains IDENTICAL (no regression).
• cargo build --release cold (clean). cargo fmt --all -- --check clean. ./scripts/check_file_size.sh exit 0.
• cargo test --release passes for perry-runtime, perry-codegen, perry-hir, perry-api-manifest.
• No new HIR Expr variant added.